Emissions and Their Implications From Heavy-Duty Diesel Vehicles and Marine Engines
- Author(s): Jiang, Yu
- Advisor(s): Cocker III, David R
- et al.
This dissertation evaluated emissions from heavy-duty diesel vehicles (HDDVs) and marine engines under a variety of different conditions. This dissertation characterizes the NOx emissions of five 2010 and newer, low-mileage, HDDVs equipped with diesel particulate filters (DPFs) and selective catalytic reduction (SCR) systems were evaluated over test cycles representing urban, highway, and stop-and-go driving on a chassis dynamometer. This information can be used to develop “zero mile” emission rates (ZMRs) for emissions inventory modes.
It is important to investigate and understand the differences between certification and in-use emission rates and to understand the factors contributing to these differences and discrepancies. This dissertation evaluated two 2010-compliant HDDVs using an engine-dynamometer, a chassis-dynamometer, and on-road. The results showed that in-use NOx emissions over urban driving cycles of chassis dynamometer, on-road testing and engine dynamometer tests were above the 0.2 g/bhp-hr certification level for both vehicles, with higher emissions for the on-road and chassis dynamometer testing. The differences between the tailpipe NOx emissions could be attributed to several factors, including differences in SCR inlet temperatures, and engine out NOx emissions. The SCR efficiencies were found to be impacted by the SCR inlet temperature. The SCR efficiencies were as a function of load, especially for the manufacturers B truck. The Not to Exceed (NTE) analysis shows that the NTE method has the limitation that it represents only a small percent of real-world operation.
The implementation of an enhanced heavy-duty (HD) Inspection and Maintenance (I/M) program could be a critical element in ensuring the emissions performance of HDDVs over their full useful life. A prototype HD I/M pilot study was conducted where the emissions of 47 vehicles were measured before and after repair. The vehicles showed good reductions post-repair for NOx for some of the higher emitting vehicles, but not significant PM reductions. Based on a review of the potential methods, a comprehensive HD I/M program was proposed with OBD as the primary methodology, remote sensing for validation testing, and mini-PEMS for dispute resolution.
It is important to understand black carbon (BC) emission factors from ships from human health and environmental perspectives. A study of instruments measuring BC and fuels typically used in marine operation was carried out on a small marine engine with and without a sampling condition (SC) system. Six analytical methods measured the BC emissions in the exhaust of the marine engine operated at two load points while burning three fuels. The results showed that both higher engine loads and higher sulfur fuels contributed to higher BC emission factors with engine load having the biggest impact on BC emissions. There was a spread of about a factor of two in the BC emissions measured by the 6 different methods. The SC system improved the comparability of some BC measurements, but only slightly.